# Black Holes

## What is a black hole?

A black hole is a place with gravity that is so extreme that nothing can escape. Proof of this is that a black hole does not emit any light because light cannot escape its gravitational pull.

## How are black holes created?

Stars have to forces acting on it, gravity and an outward acting thermal pressure. These to forces must be balanced for the star to exist. A black hole is created when there is an imbalance of these two forces and gravity wins. The star will then collapse into a small ball with the same mass it had before. The outward acting thermal pressure is thrown off balance when a star reached the end of its life and runs out of fuel. Lack of fuel means that the star cannot maintain its temperature.
Black Holes

## How do we detect black holes if they do not reflect any light?

We can detect black holes by looking for gravitational lensing. Gravitational lensing is when an objects gravity distorts the light around it. Since black holes have such a large mass they distort the light around themselves.

## How first theorized black holes?

Black holes were first theorized in 1790 by John Michell and Pierre-Simon Laplace. They calculated the mass required for an object to overcome the speed of light (keep light in). They called these invisible stars. It wasn't until 1967 that they were given the name black holes by John Weeler.

## Life Cycle of a black hole.

1) The black hole is born from a star.

2) The black hole grows by absorbing anything that comes close to it.

3) If the black hole does not come into contact with anything to absorb it will slowly shrink until it is completely die. Although this is possible this has never happened. The black hole shrinks because at a sub-atomic scale small particles are constantly being destroyed and created.

## How many black holes are there?

It is impossible to count the number of black holes in the universe but it is estimated that there is 1 black hole for every 100 stars. The closest black hole to earth is 7800 light years away, but don't worry it is a very small black holes. Small black holes are called stellar mass black holes and they make up the majority of black holes. The ratio of supermassive black holes to stellar mass black holes is 1 to 1 000 000. Black holes are still being created in our universe, but don't worry our sun does not have enough mass to one day become a black hole.

## Black Hole Myths

Black holes may or may not lead to another dimension or give us the ability to travel throw time but we will never no since we cannot get to the nearest black hole and even if we did we would not be able to communicate or leave the black hole due to its massive gravity. Black holes also do not appear out of nothing. They need a large star in order to be born. We do not have close up high resolution photos of black holes and almost all pictures that you see are made by artists. Black holes do not suck things in, in order for a black hole to grab hold of you, you would have to come within 10 miles of it.